Method of restoring a tooth

ABSTRACT

A method of restoring a tooth is provided. Method comprises the steps of dispensing a curable composition from an applicator and curing the curable composition. The applicator has a needle with a lumen. The composition is injected into a hollow on the tooth to achieve a desired shape. The composition includes curable liquid resin portion and an inorganic filler portion. The curable liquid resin portion has a polymerizable binder resin.

This is a continuation of application Ser. No. 08/646,707 filed May 6,1996 which is a continuation of Ser. No. 08/319,456 filed Oct. 6, 1994,now U.S. Pat. No. 5,547,379.

FIELD OF THE INVENTION

The present invention relates to a method for restoring a defect in atooth by using a curable composite material.

BACKGROUND

Teeth with dental decays such as cavities are generally restored byremoving the decayed area and applying a restorative thereon.Traditionally, amalgam material has been used for filling and repairingteeth. Because the amalgam material tends to harden as it is beingworked, and its thick, lumpy consistency necessitates using specializedtools for pushing the material into corners and crevices to facilitateadaptation to the tooth, its use is inconvenient and causes greatdiscomfort to the patient. Moreover the retention of an amalgamrestorative in a tooth is by bulk, for repairing a small decayed area,often an amount of healthy tooth structure many times the decayed areahas to be removed to provide room to receive the amalgam material.

The concern of the presence of mercury in amalgam material has led tothe introduction of other restoratives that do not contain mercury. Forexample, "Universal Paste" composites, such as P-SO and Z-100 sold by 3MCompany, have been used for restoring teeth. Examples of other compositematerials that can be used for repairing teeth include the compositionsdisclosed in U.S. Pat. No. 4,553,940 (Koblritz, et al) and U.S. Pat. No.5,228,907 (Eppinger, et al).

Generally, composite materials for repairing teeth are thick and sticky,making them difficult to work with and highly technical skill isrequired of the operator to properly place such materials in teeth forrestoration purposes. Universal paste type composites are generally usedby trowelling an amount of the paste into position in a hollow (or voidor cavity), tamping the paste down to improve contact with the surfaceof the cavity, carving the excessive paste into a rough outline of thedesired shape, and polishing the cured composite to a desired shape andsmoothness.

Because a composite material, similar to amalgam material, is generallyapplied as a lump in the prepared location in a tooth, voids andporosities are often incorporated into the material during placementbecause of the difficulty in manipulating the material into corners andcrevices in the tooth. Furthermore, if a composite material is lightcurable, because of the thickness of the composite material applied,incomplete polymerization often results.

Another kind of restorative material that does not contain mercury is afilm-forming composition that is generally used as a sealant, glaze, oradhesive. Typically, such a film-forming dental composition containsresins with little or no filler materials. Such filmforming dentalcompositions are typically used for sealing the tooth against cracksadjacent to fillings. Such compositions generally have low viscosity andcan be applied to the tooth by using a brush. An example of a sealant isdisclosed in U.S. Pat. No. 4,001,483 (Lee, Jr., et al.). Such acomposition is generally applied as a thin coating and when cured, formsa sealing coat on the tooth. Yet another kind of coating composite isused for masking stains and discolorations. For example, U.S. Pat. No.4,150,485 (Lee, Jr., et al) discloses a brushed on dental restorativecoating composition used for covering surface imperfections. Thiscomposition has a higher viscosity than conventional sealants. Suchfilm-forming and coating compositions have not been applied inrestoration of tooth decays such as filling cavities.

SUMMARY

The present invention provides a method of restoring a tooth that has adefect. The method includes dispensing a curable composition through aneedle with a lumen into a hollow on the tooth to achieve a desiredshape and curing the curable composition. As used herein, the term"needle" refers to a slender, hollow, stiff instrument which may bestraight, curved or bent, with or without a sharp point. The compositioncontains a curable liquid resin portion and an inorganic filler portion.The curable liquid resin portion has a polymerizable binder resin. Asused herein, a "hollow" refers to a void area or cavity that resultsafter a tooth has been prepared to receive a restorative by a cutting orabrasive tool such as a dental bur.

In another aspect, the present invention provides a method of restoringa tooth having a decayed portion including the steps of removing thedecayed portion to form a hollow in the tooth, coating the surface inthe hollow with a curable bond and curing the bond, dispensing a curablecomposition from a needle in the hollow to achieve a desired shape,curing the curable composition, and repeating the dispensing of thecurable composition and curing the curable composition until a curedstructure of desired shape and smoothness is obtained. In removing thedecayed portion, an amount of an adjacent healthy portion or the toothis removed with the decayed portion. The volume of the healthy portionremoved is about zero to three times, preferably 0.5 to 3 times thedecayed portion. The composition contains a curable liquid resin portionand an inorganic filler portion. The curable liquid portion has apolymerizable binder resin and a polymerizable diluent monomer lessviscous than the polymerizable binder resin.

The present invention provides yet another method for restoring a toothusing a composition that contains a curable liquid resin portion and aninorganic filler portion. The method includes the steps of dispensing acurable composition from a needle as one of a layer and a drop in thehollow, curing the curable composition wherein the one of a layer anddrop shrinks when it is cured, dispensing the curable composition as oneof a layer and drop on top of the cured composition and in the voidspace resulted from the shrinkage to compensate for the shrinkage, andrepeating the dispensing and curing of the composition in the hollowuntil a cured structure of desired shape and smoothness is obtained.

The method of the present invention can be advantageously utilized torestore defects in teeth. Because of the composition of the presentinvention can be applied using a hypodermic needle like tubularstructure, the composition can be applied into a small hollow in hardto-reach places on a tooth. By laying the curable composition as a thinlayer or small drop, substantially complete curing by light (as comparedto relatively incomplete curing when conventional universal paste-typeof composite is used) can be realized. Such substantial complete curingleads to improved mechanical integrity and chemical resistance of therestorative material in the tooth. Better curing leads to less stresscracking taking place in the restorative material.

The use of conventional composite material often leads to a great amountof shrinkage as the material is cured. Such shrinkage can lead to manyproblems, such as accelerated wear, open margins between the toothsurface and the filling material, leakage of foreign material into theunfilled area, thereby causing degradation and subsequent development ofcaries. In the present invention, by depositing the composition as thinlayers, curing, and repeating the process the void area left by theshrinkage of a previous cured area can be filled with a subsequent layerwith the composition, thereby eliminating or greatly reducing thepresence of unfilled areas caused by shrinkage.

The thixotropic characteristic of the restorative curable composition ofthe present invention greatly facilitates the restoration of toothwithout having to shape the composition using a scraping tool. Thethixotropic substance can be forced through a syringe and needle andcarefully deposited in a desired location and cured. By graduallybuilding up the cured structure, there is no need to remove excesscomposite material to achieve a desired shape. The relatively lowviscosity of the composition helps to spread the composition intocrevices and corners to greatly reduced amount of void area so that astrong bond can result between the composition and the tooth withoutdepending on retention of the restorative material by bulk. The lowviscosity nature of the composition, as compared to conventionaluniversal paste type composites, allows for much less manipulation ofeach increment placement of the composition. Therefore, manipulation bypaddling, pushing or prodding to place and shape the composite material(as in the case of using a universal paste) is not necessary. This makesthe composition of the present invention easier and quicker to place andresults in a less degree of discomfort to the patient. Because of theaffinity of the bond to the composition of the present invention, thecomposition is further facilitated to flow into crevices and cornersit--encounters. A drop (i.e., a dab or a bead) or a thin layer of thecomposition, when placed in a hollow, such as for Class IV restoration,will not run (i.e., flow or drip out of the hollow under gravity). Thesurface tension of the thixotropic composition is selected by varyingthe concentration of the various ingredients in the composition so as tobecome compatible with the surface of the tooth structure and to providean affinity to the bond.

The curing of the composition of the present invention provides a smoothsurface, thereby eliminating the need for finishing, polishing, andvisual inspection of margins. This, and the ability to adhere to asurface of the tooth without depending on bulk, make possible therestoration of a tooth without removing an excess amount of healthytooth structure as in a case of using amalgam or conventional universalpaste-type composite. This affords a great advantage of retaining asignificant amount of the healthy tooth structure, thereby reducing atrauma to the tooth and the likelihood of losing the tooth completelythrough multiple restorative procedures. Contrarily, the prior artmethods requires excessive removal of healthy tooth structure. Quiteoften, because of wear (i.e., abrasion) and bacterial attack through theyears, the same tooth needs to be restored many time. With excessivetooth structure removal as in the prior art methods, the tooth may beweakened to the extent that a crown or extraction is required. Themethod of present invention, being much more conservative in toothstructure removal, greatly reduces the need for such crowns andextractions.

Because no polishing is necessary to smooth the surface of therestorative structure, polishing-induced cracks, fissures, orirregularities are absent on the restorative structure. Such crevices,fissures and irregularities, if present, would increase the porosity ofthe restorative structure and lead to accelerated degradation and wear.Mechanical polishing results in scratches on the polished surface. Suchscratches, even the finest ones, increase the surface area formechanical and chemical degradation. Such scratches violate the bondingbetween the affected filler particles and the resin, which eventuallylead to the filler particles falling off. The present invention avoidssuch scratches, resulting in a longer lasting restoration on the tooth.

In the present method, a syringe-type applicator can be used to storeand deliver the composition through a needle-type tubular structure to adesired location on the tooth. Therefore, only one instrument (e.g., theapplicator with a needle) is needed for delivering and shaping thecomposition. No separate instruments are needed for performing thestorage, delivery and shaping procedures. A single drop of thecomposition can be placed precisely on a desired location, beads (ordrops) of the composition can be deposited in a line in a vertical orhorizontal direction, and a large area can be covered with a thin layerof the composition by using the syringe with a needle. Using such anapplicator, the surface of a layer of the composition can be stroked ina brush-like fashion to spread out or be teased into a peak. Because ofthe thixotropic nature of the composition, various shapes can beaccomplished by manipulating the composition with the tip of the needle.Such ease of manipulation affords great convenience to the operator inshaping the composition. Alternatively, a desired shape can be achievedby depositing the composition in small increments to build up the curedrestorative structure.

Building the restorative structure this way obviate the need to paddle,push or prod the filling material in the hollow as with the prior artmethod. This further reduces the trauma and discomfort to the patient.Furthermore, because the restorative structure is built in incrementsand requires less force, the operator (i.e., dentist) has much bettercontrol. The method of the present invention, because of its ease of useand not requiring polishing, can also be done faster than prior artmethods using amalgam material or universal paste.

By utilizing the method of the present invention, certain types of toothrestoration that have been very difficult to perform can be donerelatively easily. For example, a Class IV restoration (See examplebelow) requires the building of tools in the corner of the tooth.Amalgam generally cannot be used for this procedure. Traditional type ofpaste composite, although can be used, are very difficult to place andform into a desired geometry. When conventional methods are used, voidsand porosities often occur and require additional material to coverthem. For Class V restorations, amalgam application requires extraretention and undercuts, necessitating excessive tooth structure removaland weakening of the tooth. The use of conventional universal pastecomposite aces similar problems. Utilizing the method of the presentinvention, restoration by simply laying the composition at the preciselocation one layer or one bead at a time and curing renders theprocedure relatively easy to perform and result in a structurally sturdyand aesthetically appealing restored tooth.

BRIEF DESCRIPTION OF THE DRAWING

Illustrative embodiments of the invention are shown in the variousfigures. Throughout the figures, which are not drawn to scale to showdetails, identical reference numerals refer to identical structuralelements, wherein:

FIG. 1 shows a cross-sectional view of a tooth showing a hollow beingrestored using a syringe and needle in an embodiment of the method ofthe present invention;

FIG. 2 is a cross-sectional view of a tooth showing a hollow beingrestored with a further step of the embodiment of the method of FIG. 1;

FIG. 3 is a cross-sectional view of a tooth after restoration with theembodiment of the method of FIG. 1;

FIG. 4 is a schematic top view of a tooth after a Class I sealantrestoration;

FIG. 5 is a schematic top view of a tooth after a Class I fillingrestoration;

FIG. 6 is a schematic cross-sectional view of a tooth after a Class IIfilling restoration;

FIG. 7 is a schematic front view of a tooth after a Class III fillingrestoration;

FIG. 8 is a schematic front view of a tooth after a Class IV fillingrestoration; and

FIG. 9 is a schematic cross-sectional view of a portion of a tooth aftera Class V filling restoration.

DETAILED DESCRIPTION OF THE INVENTION

The present invention utilizes a composition for the restoration ofteeth, such as dental fillings for the repair of dental caries.

The Composition

The composition applicable in the present invention includes a curableliquid resin portion containing one or more binder resins and aninorganic filler portion having inorganic fillers. Optional ingredientsthat can be included in the composition of the present application caninclude pigments, opacifiers and the like, for improving the aestheticappearance of the composition after polymerization.

Binder resins are provided in the composition of the present applicationfor binding the various ingredients, including the inorganic fillers sothat after polymerization, the composition forms a solid, rigid,mechanically sturdy material effective for sustaining mechanical andchemical challenges which are normally encountered by the load-bearingsurface of a tooth. Binder resins suitable for such an applicationinclude ethylenically unsaturated polymerizable materials. Preferably,the resin is an acrylated polyester. Such a material may be a monomer,dimer, trimer, and the like that is polymerizable. A preferred materialis 2, 2-bis 4(2hydroxy-3-methacryloxypropoxy)phenyl! propane(hereinafter abbreviated as bis-GMA). Another material applicable ispolyurethane dimethacrylate (PUDMA). A person skilled in the art wouldunderstand that derivatives and polymers and combinations of theabove-described materials as well as other materials with similarchemical and physical properties may be utilized as the binder resin inthe composition of the present application.

Preferably, the composition applicable in the present invention alsoincludes one or more diluent monomers in an amount effective to renderthe viscosity of the liquid resin portion (which includes the binderresins and the diluent monomers) low enough to be mixed with theinorganic fillers to provide an injectable composition through a syringeneedle. Preferably, the diluent monomer can be mixed with the binderresin to have a Brookfield viscosity of less than 6,000 centipoises(cps) at 25°, more preferably between about 500 and 5,000 cps, morepreferably between about 1,000 and 5,000 cps, even more preferablybetween about 1,000 and 3,000 cps.

The diluent monomer applicable in the present application ispolymerizable. Preferably, the diluent monomers are acrylic materialssuch as 2hydroxyethylmethacrylate (HEMA), ethylene glycoldimethacrylate, diethyleneglycol dimethacrylate, triethylene glycoldimethyacrylate (TEGDMA), trimethylo propane trimethyacrylate, analogousacrylate, and the like. The more preferred diluent monomers are HEMA andTEGDMA.

Other polymerizable material that can be used as monomer or prepolymersto result in a curable liquid portion of appropriate viscosity includemethyl methacrylate and bisphenol A dimethacrylate. It is to beunderstood that a person skilled in the art will be able to device acurable liquid resin portion based on the present disclosure by usingthe above-described or other ingredients. It is believed that acomposition can be made with one or more resins that have a viscosity inthe range applicable for syringe injection as disclosed in the presentdisclosure such that the one or more resins can be considered as thebinder resin or as the diluent.

The composition of the present invention also contains a catalyst orinitiator for initiating the polymerization of the binder resin and thediluent monomer. Preferably, the polymerization of the composition ofthe present invention in initiated by a initiator system having twocomponents, an alpha diketone photosensitive species and an aminereducing agent. Examples of suitable alpha diketones for initiatingpolymerization of the composition include camphoroquinone, benzil,biacetyl, 9,10phenanthrenequinone, and naphthoquinone. Of these, thenon- aromatic alpha diketones are preferred, camphoroquinone is the mostpreferred.

A combination of an amine reducing agent with the alpha diketone resultsin a visible light sensitizing system which is applicable in thecomposition of the present invention. Amines effective for use in suchvisible light sensitizing systems include tributylamine, tripropylamine,N-alkyldialkanolamine, tryalkanolamine and acrylate derivatives such asdimethylamino ethylmethacrylate. A preferred amine is methyldiethanolamine. The use of initiators for visible light sensitizingsystems in polymerization of tooth restorative composites is known inthe art. Further, a person skilled in the art will appreciate that basedon the present disclosure, many other binder resins, diluent monomers,alpha diketones, and amines having similar chemical and physicalproperties as those disclosed above may be utilized in the compositionof the present invention.

As previously stated, inorganic fillers are included in the compositionof the present invention to impart hardness and durability to thepolymerized product. Examples of inorganic fillers suitable forapplication in the composition of the present invention include bariumaluminum silicate, lithium aluminum silicate, strontium, lanthanum,tantalum, glass, silica, quartz, and the like. Preferably, the inorganicfillers are silanated (or silanized) to facilitate bonding with thebinder resins. Other suitable inorganic fillers include alumina,zirconia, tin oxide, and titania.

Preferably, the inorganic fillers have a particle size distributioneffective for resulting in a cured product having a surface that issmooth compared to surfaces that have been polished by conventionaldental restoration technology. Generally particle size ranging fromabout 0.005 to 15 microns is applicable. Preferred inorganic fillershave a particle size of about 0.01 to 5 microns. The particle size ofthe inorganic fillers is selected so that the inorganic loading in thecompensation is effective to produce a cured product of desiredstrength, hardness and durability. Inorganic fillers of various typesand sizes can be combined (i.e. mixed) to result in a thixotropiccomposition injectable through a needle.

An inorganic filler that is particularly preferred is fumed silica,which is a colloidal form of silica. Fumed silica generally has amaximum particle size of about 0.05 micron. Although the application ofthe present invention is not limited by any theory, it is believed thatthe electron distribution around the colloidal silica facilitates theformation of hydrogen bonding, thereby resulting in a network of looselyattached particles when the colloidal silica is in an appropriateliquid. Therefore, a composition of the present invention containingcolloidal silica forms a thixotropic composition. Because of thehydrogen bonding, such a composition is relatively rigid (i.e.,viscous). When a stress is introduced into the composition, such as byshearing, the network is broken up partially, resulting in a lessviscous composition. The thixotropic characteristic of the compositionrenders it very useful for application in tooth restoration. Thecomposition can be injected through a long, thin needle such as ahypodermic needle because when pressure is applied by a syringe plungerto force the composition through the needle, the composition becomesless viscous and is dispensed through the exit opening of the needle.However, once disposed at a desired location (for example, as agenerally hemispherical dab less than about 5 mm in diameter or a layerless than about 2 mm in thickness) the composition regains its viscouscharacteristics and will not run (i.e., drip or flow other gravitationalpull).

To impact a thixotropic effect to the composition, and yet allowadequate inorganic filler to be incorporated into the curablecomposition to result in a desired hardness for restoring teeth, fumedsilica is preferably incorporated at a concentration of about 30% to70%, more preferably 40% to 60%, and even more preferably about 50% to60%, by weight of the inorganic filler material. Generally, particles oflarger than 0.05 micron (e.g., about 0.05 to about 5 microns) make upthe balance of the inorganic fillers. In a preferred mode, a smallamount of the curable composition (for example, a generallyhemispherical dab less than about 5 mm in diameter or a layer less thanabout 2 mm in thickness) can be deposited on the roof of a Class Vhollow and yet the composition will not run.

Preferably, the inorganic filler portion is a mixture of inorganicfillers of various particle size and chemical and physical properties toprovide hardness and abrasion resistance. For example, barium aluminumsilicate glass can be mixed with silicon dioxide, and glass beads ofmean particle size of 0.2 to 1 micron can be mixed with glass beads ofmean particle size of 0.01 to 0.1 micron. The amount of inorganicfillers that can be incorporated into the curable composition to resultin a particular viscosity is affected by the particle size distributionof the filler. Generally, when larger particle size fillers are used,more filler can be incorporated into the curable composition. The ratiocan be adjusted to incorporate the desired amount of inorganic fillersin the curable composition for a desired viscosity.

To produce a composition that can result in a cured product of desiredmechanical characteristics, the weight ratio of the curable liquid resinportion to the inorganic filler portion is preferably less than 7:3,more preferably less than about 1:1, even more preferably about 3:10 to1:1, and most preferably about 2:5 to 3:5.

In the curable liquid resin portion, the weight ratio of thepolymerizable binder resin to the polymerizable diluent monomer isselected so that the curable liquid portion has a viscosity of less than6,000 cps at 25° C. and such that the curable liquid resin portion whencombined with the inorganic filler portion results in a compositioninjectable by a syringe through the lumen of a needle such as ahypodermic needle (e.g. 24 gauge needle). Preferably, the weight ratioof the polymerizable binder resin to polymerizable diluent monomer isfrom about 3:1 to 1:2, more preferably from about 3:2 to 2:3.

The composition of the present invention can be cured by using visiblelight. Suitable light sources that can be used for curing thecompensation is known in art and available commercially. Generally, thepolymerization initiating system is added in a quantity sufficient topolymerize a layer of the composition disposed on a tooth in about a fewseconds (e.g. 10 seconds) of visible light exposure. Typically, thealpha diketone is added in an amount of about 0.05 to about 0.5 percentof the composition and the reducing amine is added in an amount of aboutone to five times that of the alpha diketone.

Optional ingredients, such as pigments, opacifiers, brightening agents,and other substances effective for modifying the aesthetic appeal orchemical or physical characteristics of the composition before or aftercuring can be included in the composition. Although it can be done in adifferent way, generally, the composition is made by mixing the binderresin and the diluent monomer before the addition of the initiatingsystem components. Subsequent to the addition of the initiating systemcomponents, the inorganic fillers and the optional of the ingredientsare added and mixed to form the curable composition.

Tables A and B are preferred embodiments illustrative of the compositionof the present invention. In Tables A and B, OX-50 is a silanated fumedsilica sold by DEGUSSA CORP. BA-30 is barium glass bead filler sold byINDUSTRIAL CORP. GI-2811 is an ionomer resin sold by INDUSTRIAL CORP.The ingredient 077WD (8 p) is a negative expansion filler sold byINDUSTRIAL CORP.

                  TABLE A                                                         ______________________________________                                        Formulation of Bond                                                           ______________________________________                                        Bis GMA          310 g                                                        HEMA             206 g                                                        OX-50            70 g                                                         BA-30            30 g                                                         GI-2811          25 g                                                         Camphoroquinone   1 g                                                         Amine*            3 g                                                         ______________________________________                                         *An amine such as methyl diethanolamine was used.                        

                  TABLE B                                                         ______________________________________                                        Formulation of Curable Composition for Restoration                            ______________________________________                                        Bis GMA          288 g                                                        TEGDMA           288 g                                                        OX-50            540 g                                                        BA-30            230 g                                                        077WD(8μ)     195 g                                                        Camphoroquinone   1 g                                                         Amine*            3 g                                                         ______________________________________                                         *An amine such as methyl diethanolamine was used.                        

The formulations of TABLE A and TABLE B are given as illustrations only.Other polymerizable resins and diluent monomers, as well as inorganicfillers and initiators, as previously disclosed, can be used by a personskilled in the art based on the present disclosure. For example, all theinorganic fillers in TABLE A or TABLE B can be replaced with a 5:1mixture of silanated glass (e.g. silicon dioxide) beads of mean particlesize of about 0.5 micron and silanated glass beads of mean particle sizeof about 0.05 micron

Alternatively, commercially available bonds can be used Also, for thecurable composition for restoration, a thicker universal paste typecomposite material such as P-50 or Z-100 from 3M Co. can be diluted witha diluent such as HEMA or TEGDMA to the desired viscosity. Such amaterial, although not as preferred as the composition of TABLE B, canbe used for restoring teeth with the method of the present invention.

Method of Tooth Restoration

To restore a decayed area in a tooth, first, the tooth is prepared byremoving the decayed area. Often only the decayed portion need to beremoved. However, if desired, for example, to provide more room formanipulation and inspection, healthy tooth structure less than about 4times, preferably about 0.5 to 3 times the size of the decayed portioncan be removed. More preferably, healthy tooth structure of only 0.5 to2 times the size of the decayed portion is removed so as to preservemore healthy tooth structure. Subsequently, the surface of the tooth towhich the curable composition of the present invention is to be bondedto is coated with a bonding composition (i.e. bond) such as one shown inTable A. Generally, it helps the binder resin (and therefore a curablecomposition) to bind to the tooth.

Unlike restoration using amalgam which requires bulk to secure theamalgam in place, only a small amount of healthy tooth tissue need beremoved along with the decayed portion for receiving the composition ofthe present invention. Although a large amount of healthy tooth tissuecan be removed, preferably, the amount of healthy tooth tissue removedis one to three times the size of the decayed portion. For example, whenremoving the decayed portion one cubic millimeter of tooth is removed,to prepare the tooth for receiving the curable composition, only anadditional one to three cubic millimeter of healthy tooth structureadjacent to the decayed portion is removed. Furthermore, in removingtooth structure to prepare for receiving the curable composition of thepresent invention, unlike using amalgam or thick semisolid, conventionalcomposite material, it is not necessary to create a hollow ofexcessively irregular shape or having a large opening leading into aneven larger internal volume of hollow.

After a hollow has been prepared on the tooth to receive thecomposition, the surface of the tooth in the hollow is prepared byetching with a suitable etching solution such as a 10-35 weight percentphosphoric acid. Such etching procedures are known in the art. Theetched surface of the tooth is then washed, dried and coated with abond, which is then cured. These steps, including the application of thebond and the curing thereof can be done with conventional procedures. Abond such as "SCOTCHBOND™" sold by 3M Co. can be used. However, becauseof the better chemical and physical compatibility with the restorativecurable composition of the present invention, the bond of Table A ispreferred. Referring to FIG. 1, a curable composition of the presentinvention can be applied by using an applicator 1 with a needle liketubular structure, e.g., a conventional syringe 4 with a hypodermicneedle (for example, a bent 24 gauge lour-lock needle 6 for deliveryonto the tooth. Preferably the needle has a bend to facilitate deliveryof the composition around a corner. However, needles of other size canalso be used (e.g. 25 gauge to 16 gauge), depending on the preference ofthe operator (i.e., dentist).

The composition (preferably a thixotropic composition) is preferablydelivered as a thin layer 8 (i.e., less than 2 mm thick) or a drop(preferably less than five millimeter in diameter) on the bond 10 in thehollow 12 which is on the occlusal side 13 opposite the gum 14. Becauseof the infinity of the bond 10 for the binder resins in the composition,the composition penetrates crevices and corners 16A, 16B readily.Furthermore, the compensation can be manipulated by the tip 18 of theneedle 6 to spread out in the hollow or to achieve a specific desire toshape.

If the hollow 12 is large, more than one layer 8 or drop of thecomposition may have to be applied. Before the application of anotherlayer or drop of the composition, the first layer or drop is cured by aradiation with a suitable light source (not shown).

Referring to FIG. 2, after curing, it is possible that the first layeror drop of composition might have shrunk a little. If this happens, whena second layer or drop of the composition is applied, it is applied orspread to cover the edge 20 of the first layer 8 or drop so that anycrevice or void 22 formed by the shrinkage of the first layer is filled.The second layer or drop of the composition is then cured. This processis repeated until the hollow in the tooth is completely filled and thecomposition manipulated or shaped to achieve a desired shape on thetooth (see FIG. 3). Shaping of the composition by laying the compositionand manipulating with a tip of the needle is possible because theviscosity of the composition before curing is such that when applied ina volume as described above, the composition can maintain a shapeagainst the pull of gravity.

Generally, the outermost layer 26 of the composition on the tooth 7 isshaped so that it conforms to the shape of the tooth and such that itssurface 28 is smooth. Typically, after curing, the surface 28 of therestorative material is smooth and does not require polishing.

However, if desired, the surface of the restorative material aftercuring can be polished and glazed to result in a smooth surface. Forexample, if for any reason (such as overfilling by mistake) the surfaceof the restorative material needs to be polished, after polishing, thesurface is cleaned, etched with an etching solution, washed and dried. Asmall amount of the composition can be placed on the affected area,brushed to obtain a smooth surface and cured. If there is any voids,porosities, shrinkage areas, or gaps in the margin (i.e. the areabetween the restorative material and the tooth), they can be filled andsealed with the composition as described to obtain a smooth surface.Because of the presence of a substantial amount of the inorganic fillermaterial, the cured glaze (i.e. composition) in the method of thepresent invention, unlike prior art bonds and sealants, is veryabrasion-resistant.

The following examples illustrate the application of the composition andmethods of the present invention in the restoration of defects in teeth.

EXAMPLE 1

The composition according to Table B was applied to a tooth as asealant. The occlusal pits and grooves of the tooth were slightlymanipulated with a rotating diamond instrument to clean the tooth andincrease the surface area. The surface of the tooth to be sealed wasthen prepared with a phosphoric acid solution. After etching, thephosphoric acid was washed from the tooth and the tooth was dried andcoated with the bond according to Table A by brushing. The compositionaccording to Table B was applied by means of a syringe through a 24gauge needle having a bent body without a sharp point (as shown inFIG. 1) into the pits and grooves of the tooth. The composition was thencured by a radiation with a visible light source (e.g., light of 484nanometer wavelength from a halogen light source). Referring to FIG. 4,a smooth layer of sealing coating 24 was formed on the tooth 27 coveringthe grooves 28 and crevices (not shown).

EXAMPLE 2

A Class I restoration was done with a composition according to Table B.The area of the caries in the tooth was removed until healthy toothstructure was exposed without any decayed structure remaining thereon.At this point, no further amount of healthy tooth structure was removed.The occlusal surface of the tooth was then prepared as in Example 1 withetching and coating with the bond. The composition according to Table Bwas then applied using a syringe with a 24-gauge needle similar to thatof Example 1 so that the composition flowed into the prepared area tofill the pits and grooves as well as the area where the caries had been.Referring to FIG. 5, the amount of filling material 32 was smallcompared to the tooth 37.

EXAMPLE 3

The composition according to Table B was used to restore a Class IIcavity. The decayed area of the tooth was removed so that the toothstructure was exposed without any decay structure remaining at thispoint, no further healthy tooth structure was removed. There was no needto extend the-preparation margins (i.e., the margins of tooth structuralremoval) to the lingual and buccal aspects of the tooth to provide roomfor placement of restorative material and for visual inspection of thefinished restoration. After the removal of decayed structure, the toothwas further prepared by etching and the application of a bond in amanner similar to Examples 1 and 2. The composition according to Table Bwas applied by a syringe through a 24-gauge needle similar to that ofExample 1 into the hollow resulting from the removal of decayedstructure. A thin layer (less than two millimeter thick) of thecomposition was layered on the surface at the bottom of the hollow. Thecomposition was manipulated with the tip of the needle to spread thecomposition into any crevice or corner in the hollow. The thin layer ofcompensation was then cured by irradiation with visible light in amanner similar to the above examples. Subsequently a thin layer of thecomposition was applied on top of the first layered and manipulated withthe tip of the needle so that any groove or crevice in the hollow orresulting from shrinkage of the first layer was filled with thecomposition. The second layer was then cured by radiation with visiblelight. This process of laying and curing by a radiation was repeateduntil the hollow in the tooth was completely filled. The layersweremanipulated before curing so that the restorative structure had adesired shape conforming to the original shape of the tooth. Referringto FIG. 6, the filling 45 was disposed on the occlusal side 43 of thetooth 47 opposite the gum 14. The amount of filling material was smallcompared to the tooth.

EXAMPLE 4

The composition of Table B was used to repair a Class III cavity. Thedecayed area in the tooth was removed, etched and coated with a bond ina manner similar to the above examples. The composition of Table B waslayered and cured in the hollow using a 24-gauge needle similar to thatof Example 1 in a manner similar to Example 3. However, becausegravitational force tends to pull the composition downward, the layeringwas done to gradually build up the restorative structure without thecomposition running out of the hollow to result in a shape that requiresremoval of excessive restorative material by abrasion after curing.Referring to FIG. 7, the amount of filling material 52 was smallcompared to the tooth 57.

EXAMPLE 5

The composition according to Table B was used to restore a Class IVdefect. The tooth was prepared by removing decayed structure, etchingand coating with a bond in a manner similar to the above examples. Athin layer of the composition according to Table B was applied to theprepared surface of the tooth by using a syringe and a 24 gauge needlesimilar to that of Example 1 and cured. Subsequently, additional layersof the composition were applied to the tooth, shaped by manipulationwith the syringe needle, and cured by exposure to visible light so thatthe final restorative structure conformed to the shape of the originaltooth. During the restorative procedure, some of the composition wasapplied as thin layers and some as small drops so that a desired shapewas achieved. Referring to FIG. 8, the amount of filling material 62 wasabout 30% the volume of the normally shaped tooth 67.

EXAMPLE 6

The composition according to Table B was used for restoring a Class Vdefect. The decayed tooth structure was removed, etched and coated witha bond in a manner analogous to the above examples. Thin layers or beadsof the shaped composition according to Table B were laid using a syringewith a 24 gauge needle similar to that of Example 1, shaped and cured byexposure to visible light one at a time until the hollow was filled anda desired shape conforming to the original shape of the tooth wasformed. The composition according to Table B was applied as a dab (ordrop) on the bottom (i.e. upwardly facing) surface of the hollow.Because of its thixotropic nature, the composition will not drip or runout of the hollow. The drop of the composition was then cured byexposure to visible light in a manner similar to the above examples.Subsequently, another drop of the composition was placed in the hollowadjacent to the first drop and cured. The process was repeated bybuilding up the restorative structure without leaving unfilled space inthe hollow or the composition running out of the hollow. The restorativestructure was shaped by manipulating the drops with the - needle inappropriate locations in the hollow to result in a lateral surface thatconforms to the surface of the original tooth. FIG. 9 shows the cureddrops 72 of the composition in the hollow of the tooth 77.

The present invention has been described in the foregoing specification.The embodiments are presented for illustrative purposes and are not tobe interpreted as unduly limiting the scope of the invention. It is tobe understood that modifications and alterations of the invention,especially in size and structure or in substitution of similaringredients in the composition, will be apparent to those skilled in theart without departing from the spirit in scope of the invention. Forexample, instead of utilizing photosensitive initiators for curing thepolymerization of the composition, initiators that cause polymerizationwithout the presence of light can be used. Furthermore, instead of usinga syringes, other means of forcing a thixotropic composition through aneedle-type lumen can be used. Also, instead of a constantdiameterhypodermic-needle-like instrument, an instrument with a small diameterneedle-like tube at an end thereof for position of the composition maybe used. All proportions and percentages described herein are in weightunless specified otherwise.

What is claimed is:
 1. A method for restoring a tooth,comprising:providing a hollow on a tooth having a surface for receivinga restorative composition; and applying a restorative composition to thesurface of the hollow, wherein the restorative composition comprises acurable liquid resin portion and an inorganic filler portion and has aviscosity sufficiently low to permit application to said hollow of thetooth through an applicator with an applicator needle of a size nolarger than a 16 gauge needle.
 2. The method according to claim 1including preparing the surface of the hollow by etching with an etchingsolution.
 3. The method according to claim 2, wherein the etchingsolution comprises 10-30 wt.-% phosphoric acid.
 4. The method forrestoring a tooth according to claim 1, wherein the surface forreceiving a restorative composition is prepared by etching the surface,washing the surface, drying the surface, and coating the surface with abond.
 5. The method for restoring a tooth according to claim 1, whereinthe curable liquid resin portion comprises a polymerizable acrylatedpolyester.
 6. The method for restoring a tooth according to claim 1,wherein the step of applying a restorative composition to the surface ofthe hollow is repeated to provide a desired depth of restorativecomposition.
 7. A method of restoring a tooth comprising:providing anapplicator containing a restorative composition, said applicator havinga needle with a lumen; providing a hollow on a tooth, said hollow havinga surface for receiving said restorative composition; applying saidrestorative composition to said surface by injecting said restorativecomposition into said hollow through the lumen of said needle, whereinsaid restorative composition comprises a curable liquid resin portionand an inorganic filler portion, and wherein said inorganic fillerportion includes a thixotropic agent which is present in an amountsufficient for said restorative composition to exhibit a viscositysufficiently low to pass through said lumen when exposed to anapplication pressure and sufficiently high to prevent said restorativecomposition from running after application to the hollow of the tooth;and curing said restorative composition.
 8. The method of claim 7wherein said restorative composition has a viscosity sufficiently highso that a dab of said restorative composition less than about 5 mm indiameter or a layer less than 2 mm in thickness will not run.
 9. Themethod of claim 7 wherein the viscosity of said curable liquid resinportion is from about 500 to about 5,000 centipoise at 25° C.
 10. Themethod of claim 7 wherein said applicator is a syringe having a needlewith said lumen.
 11. The method of claim 10 wherein said needle is a 16gauge to 25 gauge needle.
 12. The method of claim 7 wherein saidapplication and curing steps include applying a layer of saidrestorative composition to said surface and curing the same and thenrepeating said application and curing steps to achieve a curedrestorative structure of a desired shape on the tooth.
 13. The method ofclaim 12 including coating said surface with a curable bond and curingthe bond prior to the first of said repeated application and curingsteps.
 14. A restorative composition provided in an applicator forapplication to the hollow of a tooth through the lumen of saidapplicator, said composition comprising:a curable liquid resin portion;and an inorganic filler wherein the weight ratio of the curable liquidresin portion to said inorganic filler portion is between 7:3 and 3:7.15. The combination of a tooth restorative composition and anapplicator, said combination comprising:an applicator with an applicatorneedle of a size no larger than a 16 gauge needle; and a restorativecomposition in said applicator for application to the hollow of a tooththrough said applicator needle, said composition comprisinga curableliquid resin portion and an inorganic filler portion wherein theviscosity of said restorative composition is sufficiently low forapplication to the hollow of the tooth through said applicator needle.16. The combination of claim 15 wherein said applicator includes asyringe with the applicator needle and a lumen.
 17. The combination ofclaim 16 wherein said applicator needle is a 16 gauge to 25 gaugeneedle.
 18. The combination of claim 15 wherein said inorganic fillerportion includes one of barium aluminum silicate, lithium aluminumsilicate and strontium.
 19. The combination of claim 15 wherein saidinorganic filler portion includes one or more of barium aluminumsilicate, lithium aluminum silicate, strontium, lanthanum, tantalum,glass, silica, quartz, alumina, zirconia, tin oxide, and titania. 20.The combination of claim 15 wherein said curable liquid resin portion isabout 30% to about 70% by weight of said restorative composition. 21.The combination of claim 20 wherein said curable liquid resin portion isabout 37% to about 70% by weight of said restorative composition. 22.The combination of claim 15 wherein said applicator needle includes abend.
 23. A system for restoring a tooth comprising:an applicator with aneedle having a lumen; and a restorative composition in said applicatorfor application to the hollow of a tooth through said lumen, saidcomposition comprisinga curable liquid resin portion and an inorganicfiller portion with about 30% to about 70% by weight of the inorganicfiller portion being a thixotropic composition, and wherein the weightratio of the curable liquid resin portion to the inorganic fillerportion is less than 7:3.
 24. The system of claim 23 wherein saidthixotropic composition is colloidal silica.
 25. The system of claim 23wherein said thixotropic composition is fumed silica.
 26. The system ofclaim 23 wherein said curable liquid resin portion is about 30% to about70% by weight of said restorative composition.
 27. A system forrestoring a tooth comprising:an applicator with a needle having a lumen;and a restorative composition in the applicator for application to thehollow of a tooth through the lumen, the composition comprisinga curableliquid resin portion and a filler portion including a thixotropic agent,wherein said thixotropic agent is present in an amount sufficient forsaid restorative composition to exhibit a viscosity sufficiently low topass through said lumen when exposed to an application pressure andsufficiently high to prevent said restorative composition from runningafter application to the hollow of the tooth and before said restorativecomposition is cured.
 28. The system of claim 27 wherein said needleincludes a bend.
 29. The system of claim 27 wherein the applicatorincludes a syringe and a needle with said lumen, and wherein said needleis a 16 gauge to 25 gauge needle.
 30. The system of claim 29 wherein thecomposition forms a dab less than about 5 millimeters in diameter whenapplied to the hollow of a tooth.
 31. The system of claim 29 wherein thecomposition forms a layer less than about 2 millimeters in thicknesswhen applied to the hollow of a tooth.
 32. The system of claim 27wherein said curable liquid resin portion is about 30% to about 70% byweight of said restorative composition.
 33. A system for restoring atooth comprising:an applicator including a syringe and a needle with alumen, wherein said needle is a 16 gauge to 25 gauge needle; and athixotropic restorative composition in the applicator for application tothe hollow of a tooth, said composition being sufficiently thixotropicto exhibit a viscosity sufficiently low to pass through said lumen whenexposed to an application pressure and sufficiently high to prevent saidrestorative composition from running after application to the hollow ofthe tooth and before said restorative composition is cured.
 34. Thesystem of claim 33 wherein the composition forms a dab less than about 5mm in diameter when applied to the hollow of a tooth.
 35. The system ofclaim 33 wherein the composition forms a layer less than about 2 mm inthickness when applied to the hollow of a tooth.
 36. The system of claim33 wherein the composition comprises a curable liquid resin portion anda filler portion.
 37. The system of claim 36 wherein the curable liquidresin portion is about 30% to about 70% by weight of said composition.38. The system of claim 33 wherein said needle includes a bend.